April 3, 2020

expert reaction to use of facemasks

Comment in response to questions from journalists about the use of facemasks. 

Prof Ian Jones, Professor of Virology, University of Reading, said:

“What confuses people about mask use is whether it provides absolute protection; does it stop all virus? The answer to that, for most masks, is no. But if you ask if it stops SOME virus, the answer is yes. If an aerosol droplet hits the weave of the mask fabric rather than the hole it is clearly arrested. And lessening the aerosol dose chips away at the R0 and helps to slow the epidemic. If approved masks can be sourced there is clearly a case for making them widely available – how about at cost through the Boots tie-up just announced? They are not a cure but they address the longer flatter epidemic curve everyone is trying to achieve.” 

Infectious Disease Physician, Dr Ben Killingley said:

“In the right circumstances face masks are helpful to reduce infection transmission, they are recommended for healthcare worker use after all.

“They can be used in 2 ways by the general public;

1. An infected person wears one to reduce the output of respiratory secretions. There is some evidence to support this and it is a widely recommended practice. For example an symptomatic person could wear a mask to help prevent the spread of infection to a vulnerable household member. Of course this should not be done on its own. Distance isolation within the house and hand hygiene are at least, if not more important.

2. A non-infected person could wear a mask to try and avoid being infected, again as part of other measures mentioned above. However, the evidence that this is helpful is very weak. Studies done where household members wear a mask to protect themselves from an influenza infected household member did not find masks to be helpful overall. Possible reasons for this are that people find it difficult to be compliant with mask use all of the time and that people may start wearing the masks too late.

The other problem with the public wearing masks is that they do not have the resources available to ensure their safe use – changing them fairly often, hand hygiene frequently, taking them off safely and disposing of them safely. If a mask does its job to prevent infection, it will become contaminated on the outside. If people then touch the mask they can contaminate their hands. Hands can they spread the virus to surfaces or to a persons mucous membranes. You might argue that most mucous membranes are covered by the mask and you can’t touch them but you can transmit infection via the eye and of course people do eventually take masks off (another opportunity to self contaminate).

“So, if we could really up our game and wear masks safely without self contaminating there may be a role for them when people are around others, eg on the bus or in a shop. A vulnerable individual would derive more risk/benefit from this than a young healthy individual. However, again social distancing is key to protect vulnerable individuals, they should not be reassured that a face mask will provide all the protection they need if they mix socially.

“Wearing mask to walk down the street without coming into close contact with anyone else has no benefit at all and simply wastes resources. There is no evidence at all that the virus could or would exist in infectious amounts in outside air. Similarly futile is wearing gloves in public spaces. Gloves do not stop you touching your face and it may be that virus survives for longer on gloves than it does on skin. Hand hygiene is key and should be done on gloved hands just as often as you would for non-gloved hands.

“We should also remember that face masks are not an infinite resource and should be reserved for when they are most effective. It would not be good if we were not able to provide masks to healthcare workers because the public had consumed supplies.”

Prof Susan Michie, Director of the UCL Centre for Behaviour Change, University College London (UCL) , and Fellow of the Academy of Medical Sciences, said:

“The evidence to date shows that wearing a medical grade facemask to protect against getting viral respiratory infections such as COVID-19 is effective if you have the virus or suspect you have it or if you are caring for someone who is infected. For healthcare workers, the WHO recommends special purpose denser and well-fitting facemasks (N95 or FFP2) as they provide a stronger barrier against virus particles.

“There is not good evidence that the general population wearing a facemask will reduce transmission.  There are several explanations as to why facemasks have not generally been found to be effective if worn by the general population:

1. They do not protect against the virus getting into the eyes – only close fitting goggles do this

2. People may not fit the masks properly or take them on and off. Touching facemasks and not taking them off in the correct way may mean people contaminate their hands and spread the virus

3. People may have a false sense of reassurance and thus pay less attention to other behaviours key to reducing transmission such as social distancing and handwashing.”

Dr Stephen Griffin, Associate Professor, Leeds Institute of Medical Research, University of Leeds, and Chair, Virus Division, Microbiology Society, said:

“The subject of facemasks has been cast into the spotlight in the past few days and appears to have become a relatively polarised discussion. Whilst I’m not a clinician, public health specialist or modeller/epidemiologist, I keep being asked my view as I commented on the matter from an individual personal protection angle back in February; this feels like a very long time ago now…

“We know, based upon work done for influenza and other respiratory viruses, that paper masks afford only limited protection from droplet or aerosol transmission. The same also seems true, perhaps unsurprisingly, for improvised protection such as folded handkerchiefs, scarfs etc. Proper medical masks are obviously better, and as you move to “Filtering Face Piece” FFP2 or FFP3 masks and respirators these afford the best possible protection. However, it is critical that these more robust devices are fitted correctly as leaks can bypass any filter, regardless of its properties. Moreover, in addition to direct protection, it is generally well accepted that masks also help reduce the number of times that people touch their faces, and the wearing of masks by infected patients can limit the spread of larger droplets by “catching” coughs and sneezes, as well as encouraging better hygiene and social distancing.

“The options listed above represent a spectrum of protection, and all of them are clearly better than nothing at all. Not everyone will be able to access the more stringent protective equipment, so it’s logical to adopt the best forms of protection available. However, the recent discussion seems somewhat black and white, centring on whether all those venturing outside should wear a mask in addition to adopting social distancing and good hand/other hygiene. The answer may be to take precautions relating to the scenario in question – public transport or shops are clearly a higher risk environment compared with a solo run in the countryside, for example. Naturally, the best protection should be provided to those most at risk, namely NHS employees as well as other key workers that the rest of our society currently (and actually always) relies upon. Moreover, whilst the announcement today that FFFP3 masks are to be more widely distributed is most welcome, the ongoing shortage of PPE feels like a true low point for the support given to the NHS.

“The potential implementation of compulsory masks would only comprise one element of public health strategy and so I would expect is unlikely – by itself – to be the game changer in terms of levelling the curve and/or delaying the peak. Whilst some have pointed out that many countries that seem to have taken control over their COVID19 outbreaks have implemented such a policy, this is certainly not ubiquitous. On my one opportunity to visit China about ten years ago, I was struck by the numbers of people wearing masks in the absence of any ongoing public health scares, and yet enforcing this practice did little to stem the tide of the outbreak in Wuhan prior to full lockdown. Nevertheless, our main weapons in the fight against the SARS-CoV2 pandemic remain those of prevention, and whilst the mathematics of disease modelling is well beyond my understanding, I wonder whether when you begin to look at dynamics on a population wide scale that it may be a case of “every little helps”? Applying even small percentage-based measures to large populations accounts for considerable numbers of lives. However, bringing in such a measure will face issues in terms of compliance, enforcement, supply and cost, for what may result in little additional benefit to current measures. The simple truth is that we won’t know whether enforcing masks will make a difference to the outbreak unless we try it, combined with widespread community testing. In the absence of enforcement, providing protective masks en masse would at least give people the option to consider.”

All our previous output on this subject can be seen at this weblink: www.sciencemediacentre.org/tag/covid-19

Declared interests

None received.